Volume 447, Number 1, February III 2006
|Page(s)||221 - 233|
|Section||Interstellar and circumstellar matter|
|Published online||27 January 2006|
Search for massive protostar candidates in the southern hemisphere
II. Dust continuum emission
INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy e-mail: email@example.com
2 INAF – Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
3 INAF – Istituto di Fisica dello Spazio Interplanetario, via Fosso del Cavaliere, 00133 Roma, Italy
Accepted: 11 October 2005
In an ongoing effort to identify and study high-mass protostellar candidates we have observed in various tracers a sample of 235 sources selected from the IRAS Point Source Catalog, mostly with , with the SEST antenna at millimeter wavelengths. The sample contains 142 Low sources and 93 High, which are believed to be in different evolutionary stages. Both sub-samples have been studied in detail by comparing their physical properties and morphologies. Massive dust clumps have been detected in all but 8 regions, with usually more than one clump per region. The dust emission shows a variety of complex morphologies, sometimes with multiple clumps forming filaments or clusters. The mean clump has a linear size of ~ pc, a mass of ~ for a dust temperature K, an H2 density of cm-3, and a surface density of 0.4 g cm-2. The median values are 0.4 pc, , cm-3, and 0.14 g cm-2, respectively. The mean value of the luminosity-to-mass ratio, , suggests that the sources are in a young, pre-ultracompact Hii phase. We have compared the millimeter continuum maps with images of the mid-IR MSX emission, and have discovered 95 massive millimeter clumps non-MSX emitters, either diffuse or point-like, that are potential prestellar or precluster cores. The physical properties of these clumps are similar to those of the others, apart from the mass that is ~3 times lower than for clumps with MSX counterpart. Such a difference could be due to the potential prestellar clumps having a lower dust temperature. The mass spectrum of the clumps with masses above is best fitted with a power-law d with , consistent with the Salpeter (1955) stellar IMF, with . On the other hand, the mass function of clumps with masses is better fitted with a power law of slope , more consistent with the mass function of molecular clouds derived from gas observations.
Key words: stars: circumstellar matter / stars: formation / ISM: clouds / radio continuum: ISM / infrared: ISM
© ESO, 2006
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.